Medical catheters are used to either remove fluid from or deliver fluid to a bodily organ. Catheters have holes on the end of a tube and/or along the sides. When catheters are inserted into the body, they can clog with soft tissue. When this occurs during a procedure and the catheter no longer allows fluid flow, the catheter is normally removed, cleaned, and re-inserted. Catheters can also become clogged after implantation due to a number of causes, including ingrowth of surrounding tissue.
One disease where catheter clogging post-surgery is a major cause of treatment failure is hydrocephalus. Hydrocephalus is a disease where the brain either produces too much cerebrospinal fluid (CSF) or is unable to reabsorb it in a normal manner, increasing the intracranial pressure (ICP) within the skull. Hydrocephalus can be a congenital disease where it affects 1 in every 500 children born or can be induced by a traumatic brain injury, tumor, or a number of other reasons. Normal Pressure Hydrocephalus (NPH) is a disease developed mainly in adults over the age of 65 where the pressure is within a normal range, but there is a slight excess of CSF that can lead to cognitive disabilities.
The most common treatment of hydrocephalus is to implant a shunt to divert the excess fluid from the brain to another part of the body. Shunts generally consist of a catheter implanted in the brain (ventricular catheter), a pressure or flow-regulating valve, and another catheter, which is most commonly implanted in the peritoneum. Fluid drains from the ventricle of the brain through the proximal (ventricular) catheter out of the skull and towards the valve, which ensures that the correct ICP is maintained. Cerebrospinal fluid then passes through the distal catheter to another area of the body, such as the peritoneum, where the excess CSF is reabsorbed by the body.
These shunts can fail due to a number of causes, but the most common causes of failure are obstruction and infection. 50% of shunts will fail within the first two years after implantation, and 85% of hydrocephalus patients undergo at least two shunt revision surgeries within their lifetime. It has been found that the main cause of shunt failure is catheter occlusion, with 30.4% of shunts failing due to occlusion of the proximal end—or ventricular catheter—and 13.7% failing due to occlusion of the distal end—or peritoneal catheter. This high incidence of failure, mainly due to obstruction, leads to the treatment of pediatric hydrocephalus costing the U.S. healthcare system more than $1B every year.
Long-term obstruction of the ventricular catheter is generally attributed to slow and progressive ingrowth of the choroid plexus, a vascular semi-mobile structure of the brain located inside the ventricle. Choroid plexus is found throughout the ventricular system and is typically just adjacent to ventricular catheters when they are placed.
Short-term obstruction occurs in the first few days after surgery, leading to costly and dangerous reoperation. This phenomenon of early clogging was thought to be the product of poor catheter placement. However, recent clinical trials using video-assisted placement have not decreased the rate of short- or long-term proximal catheter obstruction or improved clinical outcomes.